Hadithcore
Mishkat al-Masabih, 1556

‘Abdallah b. ‘Amr reported God’s messenger as saying, "When a man comes to visit an invalid he should say, ‘O God, cure Your servant who may then wreak havoc on an enemy for Your sake, or walk at a funeral for Your sake’.” Abu Dawud transmitted it.

وَعَنْ عَبْدِ اللَّهِ بْنِ عَمْرٍو قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «إِذَا جَاءَ الرجل يعود مَرِيضا فَلْيقل ك اللَّهُمَّ اشْفِ عَبْدَكَ يَنْكَأُ لَكَ عَدُوًّا أَوْ يَمْشِي لَكَ إِلَى جِنَازَةٍ» رَوَاهُ أَبُو دَاوُدَ

References1 variant
In-Book Reference
Book 5, Hadith 34